Process of preparing cyclohexyland benzyl-amino mercapto-benzothiazoles



Patented Feb. 27, 1940 UNITED STATES PATENT OFFICE PROCESS OF PREPARINGCYCLOHEXYL- AND BENZYL-ADHNO MEBCAPTO-BENZO- THIAZOLES No Drawing.

Original application October 16,

1937, Serial No. 169,473. Divided and this application July 20, 1938,Serial No.

13 Claims (CL 260-406) The present invention relates to a new class ofrubber vulcanization accelerators and to rubber vulcanized in thepresence thereof. More particularly it relates to the condensationproducts l 01' mercapto aryl thiazoles and primary amines.

In accordance with the preferred embodiment of the present invention ithasbeen discovered that mercapto aryl thiazoles, as for examplemercaptobenzothiazole, mercaptonaphthothiazole,mercaptophenylbenzothiazole, or substituted mercapto aryl thiazoles, forexample mercaptomethylbenzothiazole,mercaptochlorbenzothiazole, andmercaptoaminobenzothiazole may be condensed with primary amines of theclass which is exemplified by cyclohexyl and benzyl amines 15 to producea new class of rubber vulcanization accelerators.

Examples of the preferred class 01' materials are benzyl amino thiobenzothiazole; cyclohemlamino thio benzothiazole; p-methylcyclohexylamino thio benzothiazole; cyclohexylamino thio 4 phenylbenzothiazole; benzyl amino thio 4 phenyl benzothiazole; p-ethylcyclohexylamino thio benzothiazole; hexahydrobenzylamino thiobenzothiazole; and cyclohexylamino thio 4 methyl benzothiazole.

The following are to be understood as illustrative embodiments of theinvention and not limitative of the scope thereof.

Exmrn: I

Substantially 472 parts by weight (substantially 0.25 molecularproportion) of sodium mercaptobenzothiazole dissolved in water to form asolution of substantially 394 c. c. in volume was mixed with 25 parts byweight (substantially 0.25 molecular proportion) of cyclohexylamine. Asecond solution was prepared by mixing 35.2 parts by weight(substantially .275 molecular pro- 40 portion) of 30% by volume hydrogenperoxide and 94.5 c. c. (substantially 0.115 molecular proportion) of2.437N sulfuric acid. This latter solution containing the peroxide wasadded with good stirring to the first solution during a period or 25-30minutes, the temperature of the reaction mixture being maintained at -55C. Stirring was continued for a short time after the addition of theperoxide solution and then 30 c. c. oi! 10% caustic soda (substantially0.075 molecular proportion) was added and the mixture ball milled for 4hours, filtered, washed free or alkali and dried at 60 C. A good yieldof cyclohexylamino 2 thio benzothiazole was obtained. The reactioninvolved is as follows:

The cyclohexylamino 2 thio benzothiazole melted at 103-104 C. Analysisfor nitrogen and sulfur gave the following results:

Theory (calculated (or Found CuHu I I) Percent Percent Nitrogen 10. 6010. 10. 58 Sulfur 24. 26 24. 40 24. 42

The cyclohexylamino 2 thio benzothiazole described above wasincorporated in the usual manner in a typical rubber gum stockcomprising Pale crep 100 Zinc mzide 8 Sulfur 2.5 vStearic d 0.5cyclohexylamino 2 thiobenzothiazole 0.5

The rubber stock thus compounded was vulcanized and the cured rubberproduct tested with the following results.

Table I Modulus of elasticity Cure in lba/in. at elonga- Tensile at Ult.

break in oioug., Lb! lbsJin. percent Mins. steam 500% 700% pressureshowed no set-up" or pre-vulcanization when tested with a Williamsplastometer described by Williams, Industrial and Engineering Chemistryfor 1924 (vol. 16, p. 362-see also Krall ibid., vol. 16, p. 922) afterheating for 60 and 120 minutes at 200 F.

Cyclohexylamino 2 thio benzothiazole was also employed in a typicalrubber tread stock compris-. ing

Smoked sheets 100 Carbon black 50 Zinc nxidP 5 Sulfur" I 3 Stearic acid3 Pine tan 2 p-Amino diphenyl-acetone condensation product 1Cyclohexylamino 2 thio benzothiazole 0.75

The compounded rubber stock on vulcanizing and testing gave thefollowing results for the unaged stock.

Table II Modulus of elasticity Cure in lbsJin. at elongaor- Tensile atUlt.

in elong., mm lbsJin. percent Mins. steam 200% 400% pressure Thefollowing results were obtainedafter air bomb aging the above describedvulcanized stock at 220 F. for 9 hours with 50 lbs. air pressure.

Table III Modulus of elasticity Cure in lbs/in. at elonga- Tensile aton.

break in elong., mm Illa/in. percen Mins. steam 200% 400% ressure Thedata'set forth in Tables II and III show that the new class ofaccelerators, for example cyclohexylamino 2 thio benzothiazole arelikewise remarkably eflicient in rubber tread stocks.

The flex cracking resistance of the above described vulcanized treadstock was determined on a flexing machine as set forth by L. V. Cooper,Analytical Edition of Industrial and Engineering Chemistry, vol. 2, No.4, 1930, pages 391-394 and both the unaged stock and the stock after 7days aging in the Geer oven at 70 C. were found to be markedly resistantto flex cracking.

' Exam!!! Substantially 47 parts by weight (substantially 0.25 molecularproportion) of sodiummercaptobenzothiazole dissolved in substantially350 parts by weight of water was mixed with 27 parts by weight(substantially 0.25 molecular proportion) of benzyl amine. A secondsolution was prepared comprising 35.2 parts by weight (substantially0.275 molecular proportion) of 30% by volume hydrogen peroxide and 93 c.c. (substantially 0.115 molecular proportion) of 2.484N sulfuric acid.The peroxide solution was added over a period of thirty minutes to thewell agitated benzyl amine-sodium mercaptobenzothiazole solution,keeping the temperature of the mixture at 45-50 C. Following theaddition stirring was continued for 10 minutes, 30 c. c. of 10% causticsoda solution added, and the charge ball milled for 4 hours. Thecolorless reaction product was filtered ofl, washed free of alkali anddried at 60 C.- The melting point of the dried material was 114-116" C.and was obtained in a good yield. After recrystallizing from alcohol themelting point was 117-118". The above described benzyl amino 2thiobenzothiazole was incorporated-in a typical rubber stock comprising:

Pale crepe 100 Zinc oxide 5 Sulfur 3 Stearic aci 1 Benzylamino 2 thiobenzothiazole 0.75

After vulcanizing the cured rubber product was found to possess thefollowing tensile and modulus characteristics.

thiobenzothiazole exhibits the desirable properties typical of thepreferred class of materials.

EXAMPLE III Substantially 47 parts by weight (substantially 0.25molecular proportion) of the sodium salt of 2-mercapto 4-methylbenzothiazole, dissolved in substantially 400 parts by weight of water,was mixed with 25 parts by weight (substantially 0.25 molecularproportion) of cyclohexylamine. A second solution was preparedcomprising 35.2 parts by weight (substantially 0.275 molecularproportion) of 30% by volume hydrogen peroxide and 93 c. c.(substantially 0.115 molecular proportion) of 2.484N sulfuric acid. Theperoxide solution was added over a. period of thirty minutes to the wellagitated cyclohexylamine-sodium mercapto 4-methyl benzothiazolesolution. After stirring for ten minutes longer the product wasseparated by decanting oil the upper aqueous layer and taken up in 250c. c. of ether, washed thrice with 200 c. 0. portions of 2% caustic sodasolution, then repeatedly with-distilled water.

Pale crepe 100 Zinc oxide 5 Sulfur 3 Stearic acid 1 Cyclohexylamino 2thio 4-methyl benzothiazole 0.75

After vulcanizing thecured rubber product was found to possess themodulus and tensile characteristics given in Table V.

Further examples of the preferred class of materials are obtainable byutilizing the principles hereinbefore set forth. For example the sodiumsalt of 2-mercapto 4 phenyl benzothiazole on condensing withcyclohexylamine forms a condensation product falling within the scope ofthis invention and the condensation product so obtained whenincorporated in a typical rubber stock exhibits the desirable propertiescharacteristic of the preferred class of materials.

If desirable the new and improved class of accelerators may be employedin conjunction with basic nitrogen containing accelerators. Thus onemploying ,cyclohexylamino thio benzothiazole in conjunction withdiphenyl guanidine the former is thereby activated and the acceleratingaction increased. The test data also revealed that diphenyl guanidinephthalate used in conjunction with one of the preferred class ofaccelerators gives an especially valuable accelerator combination. Otherbasic nitrogen containing accelerators as for example triphenylguanidine and di ortho tolyl guanidine may be similarly employed. As aspecific example of the desirable properties of the preferred class ofmaterials when activated by a basic nitrogen containing accelerator, thefollowing dry heat stocks were compounded:

Stock B The stocks so compounded were cured in dry heat at 260 F. andthe following modulus and tensile properties found on testing the curedstock.

Table VI ta e r Dry heat cure y n Tensile Ult. stock :Lalongauons atbreak elong.,

11 perlbsJinJ cent Mins. Temp. 300% 500% F B 200 520 1760 2890 595 A 60200 424 1430 2730 620 B 60 260 505 1675 2840 595 The above data showthat the preferred class of materials, for example cyclohexylamino thiobenzothiazole, may be used in conjunction with basic nitrogen containingaccelerators, for example diphenyl guanidine, to produce an improvedaccelerator combination and more particularly a combination in which thepreferred class of materials are strongly activated by the basicnitrogen containing accelerator.

Other methods of preparing the preferred class of accelerators may beemployed than those hereinbefore set forth. As is apparent to thoseskilled in the art other means of effecting the oxidation may beutilized. The invention is not limited by the temperatures and reactiontimes mentioned specifically and other oxidizing agents than hydrogenperoxide may be employed. Furthermore, there are other methods ofisolation and purlflcation of the product. For example the ball millingof the reaction mixture with caustic soda as described in Example I hasbeen found to be an effective and practical means of purifying theproduct and driving the reaction to completion, but it is likewisepossible to dissolve the product in an organic solvent, as for exampleether, and thus remove insoluble impurities. Where convenient ordesirable a recrystallization step may be introduced and the productrecrystallized from an organic solvent, as for example alcohol. Theresidue after removing the reaction product may be worked up to recoverany unreacted mercaptoarylthiazole. Thus the filtrate in Example I wasacidified and unreacted mercaptobenzothiazole filtered ofi.

The present invention is limited solely by the appended claims.

This application is a division of my co-pending application Serial No.169,473 filed October 16, 1937.

What is claimed is:

1. A process for the production of a chemical product comprisingcondensing a mercaptoarylthiazole containing an SX group in the 2position, X being selected from a group consisting'of hydrogen and metaland a primary amine selected from the class consisting of a cyclohexyland benzyl amines in the presence of an oxidizing agent.

2. A process for the production of a chemical product comprisingcondensing a mercaptoarylthiazole containing an SX group in the 2position, X being selected from a group consisting of hydrogen and metaland a primary amine selected from the class consisting of a cyclohexyland benzyl amines in the presence of an oxidizing agent and a strongsubstantially nonoxidizing mineral acid.

3. A process for the production of a chemical product comprisingcondensing a soluble salt of a mercaptoarylthiazole and a primary amineselected from the class consisting of a cyclohexyl and benzyl amines inthe presence of a mild oxidizing agent.

4. A process for the production of a secondary amino 2-thioarylthiazolecomprising condensing an alkali metal salt of a mercaptoarylthiazole anda primary amine selected from a class consisting of a cyclohexyl andbenzyl amines in the presence of hydrogen peroxide.

5. A process for the production of a secondary amino 2-thioarylthiazolecomprising condensing an alkali metal salt of a mercaptoarylthiazole anda primary amine selected from the class consisting of a cyclohexyl andbenzyl amines in the presence of hydrogen peroxide and a quantity of astrong substantially non-oxidizing acid substantially equivalent to thealkali metal salt initially employed.

6. A process for the production of a secondary amino 2-thioarylthiazolecomprising condensing an alkali metal salt of a mercaptoarylthiazole anda primary amine selected from the class consisting of a cyclohexyl andbenzyl amines in the presence of hydrogen peroxide and a quantity ofsulfuric acid substantially equivalent to the alkali metal saltinitially employed.

'7. A process for the production of cyclohexylamino 2-thiobenzothiazolecomprising condensing the sodium salt of Z-mercaptobenzothiazole withcyclohexylamine in the presence of hydrogen peroxide and a quantity ofsulfuric acid substantially equivalent to the alkali metal saltinitially employed.

8. A process for the production of benzylamino 2-thiobenzothiazolecomprising condensing the sodium salt of 2-mercaptobenzothiazole withbenzylamine in the present of hydrogen peroxide and a quantity ofsulfuric acid substantially equivalent to the alkali metal saltinitially em ployed.

9. A process for the production of cyclohexylamino 2-thio 4-phenylbenzothiazole comprising condensing the sodium salt of Z-mercapto 4-phenyl benzothiazole with cyclohexylamine in the presence of hydrogenperoxide and a quantity of sulfuric acid substantially equivalent to thealkali metal salt initially employed.

10. A secondary amino 2-thioarylthiazole wherein the sulfur in the 2position is linked to a nitrogen atom which is additionally linked tohydrogen and to a member of a group consisting of cyclohexyl and benzylradical.

11. Cyclohexylamino 2-thio benzothiazole of the structure l2. Benzylamino z-thiobenzothiazole of the structure 13. Cyclohexylamino 2-thio4-phenylbenzothiazole of the structure MARION W. HARMAN.

